Want to legally migrate to the U.S.? It might take 24 years.

We take a look at the long wait for a permanent residency visa

Republican presidential hopefuls are elbowing each other to prove who has the harshest plan for deporting undocumented immigrants. Some have said that people need to “get in line” and apply to migrate to the U.S. legally.

But that line is not single file. In fact, it’s very, very long — there’s more than 4.4 million applicants already in it.

The U.S. limits how many people can migrate legally — most are either family members of U.S. citizens or permanent residents, or arrive on an employment visa. The demand to get in has outpaced the number of available permanent residency visas every year since the limits went into effect in 1965, according to the non-partisan Migration Policy Institute.

How quickly your application is processed has a lot to do with how many other people from your country of origin are also looking to move. The U.S. has a rule where no one country can make up more than 7% of immigrants allowed in each year. Yet, people from Mexico make up 30% of the applicants. Which means a really long wait for them.

Other relatives have shorter wait times depending on their country of origin, and the limits for each family-based category. (For children under the age of 18, spouses and parents of U.S. citizens, these wait times don’t apply. In those categories, there is no limit to the number who can move to America.)

One other category not included is refugees — or people who can’t return to their home country because of high risks of persecution. The U.S. has an annual limit of 70,000 refugees admitted per year, but Secretary of State John Kerry recently announced plans to up that quota to 100,000 by 2017 as the crisis in Syria has intensified.

The only other way to skip the line is by entering the “visa lottery.” The U.S. has something called a “Diversity Visa Program” that allows people from certain countries with less demand to apply, if they meet specific qualifications (i.e. a high-school education, two years of professional experience). They are distributed on a regional basis, and the most recent 2014 report found that most of these immigrants are from Africa.

So, it’s not as simple as people “getting in line.”

It’s a little about luck, and a lot about how popular the idea of leaving is in your country. Some candidates, like Sen. Lindsey Graham, have proposed reforming legal migration. With an average 19-year backlog of people waiting for a visa, he’s probably onto something.